noun · 5 senses · updated from the 2026-07-25 local source snapshot
Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.
Sound
Pronunciation
Each Play button uses your device's default local English voice, or a natural local fallback. The selected voice name appears after playback. This is synthesized speech, not a source recording.
/ɪˈfɛk.tɪv.nɪs/weak vowel distinction
US:Recorded audio is listed in the source snapshot.
/əˈfɛk.tɪv.nəs/weak vowel merger
CMU ARPABET:IH0 F EH1 K T IH0 V N AH0 S
Digits mark lexical stress: 1 primary, 2 secondary, 0 unstressed.
CMU ARPABET 2:IY1 F EH0 K T IH0 V N AH0 S
Digits mark lexical stress: 1 primary, 2 secondary, 0 unstressed.
1
noun
Meaning 1
The property of being effective, of achieving results.
Definition source: English Wiktionary via Wiktextract
Usage: countable, uncountable
Examples
The effectiveness of the drug was well established.
Meaning relationships
Synonyms: none provided
Antonyms: none provided
2
noun
Meaning 2
The capacity or potential for achieving results.
Definition source: English Wiktionary via Wiktextract
Usage: countable, uncountable
No example sentence was provided for this meaning.
Meaning relationships
Synonyms: none provided
Antonyms: none provided
3
noun
Meaning 3
The degree to which something achieves results.
Definition source: English Wiktionary via Wiktextract
Usage: countable, uncountable
Examples
He questioned the effectiveness of the treatment.
Meaning relationships
Synonyms: none provided
Antonyms: none provided
4
noun
Meaning 4
capacity to produce strong physiological or chemical effects
Definition source: Princeton WordNet 3.0
Examples
the toxin's potency
the strength of the drinks
Meaning relationships
Synonyms: potency, strength
Antonyms: none provided
Broader terms: power, powerfulness
5
noun
Meaning 5
power to be effective; the quality of being able to bring about an effect
Definition source: Princeton WordNet 3.0
No example sentence was provided for this meaning.